In fact, global warming made the ancient mountain conifers easier for the study team to find.

"For many millennia they survived in the mountain tundra as low-growing shrubs perhaps less than a meter high," Kullman said. "Now they are growing up like mushrooms—you can see them quite readily."

Rising Timberline

But climate change could also swamp these living Ice Age relics, he warned.

The treeline has climbed up to 655 feet (200 meters) in altitude during the past century in the central Sweden study area, the team found.

"A great change in the landscape is going on," Kullman said. "Some lower mountains which were bare tundra less than a hundred years ago are totally covered by forest today."

Mountains tend to provide a refuge for the planet's most venerable trees because of reduced competition from neighbors and other plants and because the sparser vegetation around the timberline is less vulnerable to forest fires, Kullman said.

Another factor is reduced human impacts such as logging, said Tom Harlan of the Laboratory of Tree-Ring Research at the University of Arizona.

"Human activity lower down has demolished all sorts of things that could have been extremely old," he said.